The bill, which has bipartisan support, would impose strict penalties on buyers and sellers involved in purchases of firearms for someone who can't legally buy one.

WASHINGTON — The Senate will take up its first firearms measure since the Newtown, Conn., school shooting, after the Judiciary Committee approved a bill Thursday to combat gun trafficking.

The proposal, steered by Sen. Patrick J. Leahy (D-Vt.), the committee chairman, would impose strict penalties for buying a firearm for someone who cannot legally do so, an act known as a straw purchase. The bill would also toughen punishment for selling a gun to a person prohibited from owning one.

"Law enforcement officials have consistently called for a firearms trafficking statute that can be effective to go after straw purchasers," Leahy said. "What we need to do now is to create better law enforcement tools."

The trafficking bill, one of four gun measures being debated by the committee, will now move to the Senate floor. It faces an easier path than background checks for all gun sales and a ban on assault weapons and high-capacity magazines. Those bills, which the committee is to consider next week along with a school safety measure, have so far failed to garner the bipartisan support needed to pass the Senate.

President Obama, who made gun control one of his top priorities after a gunman killed 20 first-graders and six faculty members at Sandy Hook Elementary School in December, called the vote a "big step toward sensible gun safety reforms." He said the bill would "crack down on folks who buy guns only to turn around and funnel them to dangerous criminals."

The measure passed on an 11-7 vote; all 10 Democrats on the committee backed the bill, along with Sen. Charles E. Grassley of Iowa, the top Republican. Grassley's support came after weeks-long negotiations with Democrats. But some other Republicans on the committee withheld their approval.

"My concern is this bill is a solution in search of a problem," said Sen. John Cornyn (R-Texas). Noting that there are laws already on the books meant to deter straw purchases, he said, "I have a hard time explaining to constituents how passing more laws that will go unenforced makes them any safer."

Under current law, prosecutors can charge straw purchasers with illegally making false statements on federal firearms sales forms, which carries a penalty of up to 10 years in prison or up to $250,000 in fines.

But law enforcement officials say the charge is often viewed as a paperwork violation, which hurts their ability to clamp down on such activity. The proposed bill would define straw purchases as a crime and raise the sentence to as much as 15 years imprisonment, or up to 25 years if it can be shown that the buyer had reason to believe the gun would be used in a violent crime. Federal law bars gun ownership for certain people, such as felons and those who have been involuntarily committed because of mental illness.

David Chipman, a former special agent at the Bureau of Alcohol, Tobacco, Firearms and Explosives, said the tougher law would be a stronger deterrent, establishing a "clear standard" that illegally buying a gun for another person is "morally reprehensible."

"The way we had been prosecuting did not make that clear. Over 25 years, I saw on a daily basis pretty normal people being willing to buy a gun for another person," said Chipman, who now works with the nonprofit group Mayors Against Illegal Guns.

The National Rifle Assn., the nation's most influential gun rights group, signaled Thursday that it also believed straw purchases and trafficking should be addressed.

"We're supportive of efforts to try and tackle this," said Andrew Arulanandam, the group's spokesman. He called the Leahy bill "a step in the right direction," but he also said the NRA did not support the bill in its current form. He said it included some provisions that were excessively broad. For example, he said, the bill's forfeiture provision could enable law enforcement to seize a firearm dealer's entire inventory.

The NRA critique was notably mild compared with the fiery rhetoric often heard from the group's leadership.

The measure already has the support of two Republicans besides Grassley: Sens. Susan Collins of Maine and Mark Steven Kirk of Illinois. With that bipartisan support, the bill is seen as likely to pass the Senate.